The present invention relates to cutting members such as blades for cutting both circular and non circular cross-sections, and in particular to blades and cutting machines for cutting roller blinds and the like.
Machines and blades used for cutting through elongate members such as roller blinds have been known for many years. Typically, such a device is used in department stores to produce blinds of a specific width from a stock of ready-to-use blinds. The roller tube is usually made in two sections, one of rolled formed metal and the other of cardboard. Due to the ease in slicing through cardboard, this is generally the section that is trimmed. The idle end plug is removed and the roller blind is inserted into a circular opening in the cutting machine. A circular blade in the machine cuts through both the fabric and cardboard tube of the blind and upon completion the idle end plug is reinserted. The blade used in such a machine is a circular knife blade that is held against the fabric surface by a weight acting through a pivot. This is known as a blade-arm-weight assembly which is connected to a back plate and is driven in a circular path by an electric motor. As the cutter progresses the blade is pushed further into the fabric and cardboard by the weight under the action of the centrifugal force.
However, such machines are totally inadequate for cutting through non-circular cross-sections, or through any material other than say fabric or cardboard. The circular blade tries to follow the rapidly changing surface contours of say a rectangular blind as it travels around a circular path resulting in a deformed and unsatisfactory cut. The applicant has discovered that providing a cutting edge which contacts with the surface to be cut at least two points results in a smooth cut regardless of the shape of the cross-section.